fix(calendar): the example logic judgment is incorrect (#3442)

src/calendar/_example/calendar.wxs

@@ -1,23 +1,25 @@
 function getDateByTimestamp(val) {
   var date = getDate(val);
-  return [date.getFullYear(), date.getMonth() < 10 ? '0' + ( date.getMonth() + 1) : date.getMonth() + 1, date.getDate() < 10 ? '0' + date.getDate() : date.getDate()].join('-');
+  var month = date.getMonth() + 1;
+  var day = date.getDate();
+  return [date.getFullYear(), month < 10 ? '0' + month : month, day < 10 ? '0' + day : day].join('-');
 }
 
 function formatTimestamp(val) {
   if (!val) return '';
 
   var i = 0;
-  if(val.constructor && val.constructor == 'Array'){
+  if (val.constructor && val.constructor == 'Array') {
     var _str = '';
     for (var len = val.length; i < len; i++) {
       _str += getDateByTimestamp(val[i]) + '、';
-    };
-    return _str
+    }
+    return _str;
   }
 
   return getDateByTimestamp(val);
-};
+}
 
 module.exports = {
-  formatTimestamp: formatTimestamp
-}
+  formatTimestamp: formatTimestamp,
+};